Boot Camp Fail. Genius Bar struggling

I have been trying to install BootCamp onto my 2013 iMac. However, I cannot get past failed partition "Your disk could not be partitioned. An error occurred while partitioning the disc." The closest I have come was after the Fusion Drive was replaced, I tried to make a 200GB partition and it got 3/4 the way through. That is the ONLY time partitioning has even remotely worked.

Among thing I have tried

• Terminal DiskUtil shows all the correct disks and no phantoms.
• Zapped PRAM
• Disk Utility from Recovery Mode
• /sbin/fsck -fy
• One time, I found the partition mount points and I saw what appeared to be a Windows partition, I did something and it was gone. I literally cannot remember what commands I used to get that view, how I started up or anything.

Genius Bar

• I have visited the Genius Bar 3 times. Every time, the techs put it through the triage and all systems check out fine. The 1st time ended with the tech believing there was a tech memo on the era Fusion Drive I have. So they had it replaced.
• Interestingly, I learned that Apple does not make a way to unmount the fusion drive. The triage the techs need to use is an older OS version (including use of the old DU)
• This last time, the tech decided to kick the problem up a tier.

Suspicions

• I bet the BCA does not play nicely with Fusion Drive in 10.11.5. I think it is such a niche issue, it is not widely reported.
• I suspect there is a ghost partition(s) from my many failed partition attempts.

System Details

• 27 inch Later 2013
• 3TB Fusion Drive (1.66 TB available)
• El Cap 10.11.5